batman-adv: Fix multicast TT issues with bogus ROAM flags

[ Upstream commit a44ebeff6bbd6ef50db41b4195fca87b21aefd20 ]

When a (broken) node wrongly sends multicast TT entries with a ROAM
flag then this causes any receiving node to drop all entries for the
same multicast MAC address announced by other nodes, leading to
packet loss.

Fix this DoS vector by only storing TT sync flags. For multicast TT
non-sync'ing flag bits like ROAM are unused so far anyway.

Fixes: 1d8ab8d3c176 ("batman-adv: Modified forwarding behaviour for multicast packets")
Reported-by: Leonardo Mörlein <me@irrelefant.net>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index e14f7c6436b4c478e64867f51a880d3ec35156aa..0f4d4eece3e4deca20f3e6531fba13d4dbe005bf 100644 (file)
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1679,7 +1679,8 @@ static bool batadv_tt_global_add(struct batadv_priv *bat_priv,
                ether_addr_copy(common->addr, tt_addr);
                common->vid = vid;
 
-               common->flags = flags & (~BATADV_TT_SYNC_MASK);
+               if (!is_multicast_ether_addr(common->addr))
+                       common->flags = flags & (~BATADV_TT_SYNC_MASK);
 
                tt_global_entry->roam_at = 0;
                /* node must store current time in case of roaming. This is
@@ -1743,7 +1744,8 @@ static bool batadv_tt_global_add(struct batadv_priv *bat_priv,
                 * TT_CLIENT_TEMP, therefore they have to be copied in the
                 * client entry
                 */
-               common->flags |= flags & (~BATADV_TT_SYNC_MASK);
+               if (!is_multicast_ether_addr(common->addr))
+                       common->flags |= flags & (~BATADV_TT_SYNC_MASK);
 
                /* If there is the BATADV_TT_CLIENT_ROAM flag set, there is only
                 * one originator left in the list and we previously received a